Is there a way to replace an object in my scene with a different one?
If the objects are all of the same type (mesh, curve, empty, etc) you can use the make links menu.

Select all objects you want to replace, then Shift-Select the "master object" you want to replace with making sure it remains as Active Object.

Then press Ctrl + L Make links > Object Data.

You can also access it from the Object > Make Links > Object Data menu in the 3DView header.

If objects are empties with duplicated collections use the Instance Collection option instead.